Field of the Disclosure
Embodiments of the present disclosure generally relate to magnetic memory devices having enhanced perpendicular magnetic anisotropy.
Description of the Related Art
Magnetic memory devices in which the magnetic moment is orientated approximately perpendicular to the magnetic layer can achieve smaller device dimensions and greater overall storage capacity than memory devices where the magnetic moment is orientated in the plane of the magnetic layer. In order to effectively operate, memory devices require thermal stability of the perpendicular magnetic moment orientation. Perpendicular magnetic anisotropy (PMA) is critical in maintaining the thermal stability of the data stored in magnetic memory devices. Traditionally, magnetic memory cells consist of a fixed magnetic reference layer, a tunneling layer, and a free magnetic layer. The magnetic moment of the fixed layer is typically pinned by an adjacent antiferromagnetic layer. As the magnetic magnetization direction of the free layer changes relative to the reference layer, this change is detectable as a change in electrical resistance of the device, known as the tunneling magnetoresistance (TMR). The interfaces with the tunneling layer, in some configurations (Fe/MgO/Fe or FeCo/MgO/FeCo), can provide some PMA for the memory cell. However, the presence of disorder and crystallinity mismatch at the interface of the ferromagnetic and tunneling layers can lead to reduced PMA and poor TMR. Furthermore, there is an interest towards the production of smaller memory devices so that higher storage capacity can be achieved. These smaller memory devices will require greater PMA in order to maintain thermal stability of the magnetic moments.
The addition of layers consisting of heavy nonmagnetic elements or layers, which increase the moment on the free layer, has been proposed to promote PMA. However, these additional layers increase the critical current necessary to flip the magnetization and result in decreased device performance and increased energy consumption during writing and erasing operations.
Therefore, there is a need in the art for a memory cell having enhanced perpendicular magnetic anisotropy.